data table

Question

DataTable t;
t=a.hello();
dropdownlist.datasource=t;
dropdownlist.DataTextField  = "c1"; 
dropdownlist.DataValueField = "c2";
dropdownlist.DataBind();

Answer 1

DataTable是一般类型，tmp是具有模式的DataTable.return时应这样写
return (DataTable)tmp

Answer 2

class  a
{
   public static DataTable hello()
      {
                   DataTable tmp=new datatable();
                   DataColumn tmp1=new DataColumn("c1",typeof(char(15));
                   DataColumn tmp2=new DataColumn("c2",typeof(char(15));
                   tmp.column.add(tmp1);
                   tmp.column.add(tmp2);
                   DataRow t;
                   t=tmp.NewRow();
                   t["0"]="dddddd";
                   t["1"]="aaaaaa";                   tmp.Rows.Add(t);                   tmp.acceptchanges();
                   return tmp;
      }
}DataTable t;
t=a.hello();
dropdownlist.datasource=t;
dropdownlist.DataTextField  = "c1"; 
dropdownlist.DataValueField = "c2";
dropdownlist.DataBind();